Metal body resistant to fluctuating stresses



June 4, 1935.

' H. W. GRAHAM El AL METAL BODY RESISTANT TO FLUCTUATING STRESSES Filed March 28, 1955 INVENTORS M w-M g/4 MZM J 2 Y6,

Zone of Cold Work Patented June 4, 1935 PATENT OFFICE METAL BODY RESISTANT T0 FLUCTUATING STRESSES Herbert W. Graham and Samuel L. Case, Pittaburgh, Pa., assignors to Jones & Laughlin Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application March 28, 1933, Serial No. 663,155

5 Claims.

This invention relates to metal bodies resistant to fluctuating stresses and is hereby particularly described as applied to a drill pipe, although it has numerous other applications:

To take the example stated, drill pipes are subjected to severe and continuing fluctuating stresses, and in practice they frequently fail prematurely. The failure is highly objectionable not only because of the shortened life of the drill pipe but also because, it often takes place while the string of drill pipe is in the ground, frequently causing lost time and considerable expense for fishing. The threads constitute relatively sharp changes in surface conflgurationof the drill pipe and it has been observed that failures of bodies subjected to fluctuating stresses are generally initiated at such point.

We have found that these defects may be overcome by making the body of steel having special characteristics, and subjecting it, particularly in those portions where failure is most likely to ocour, to a special treatment; which we have found greatly enhances the life of the article.

We use a non-aging steel which may be obtained, for example, by adding aluminum to the steel in the amount of one to three pounds per ton; or an equivalent amount of an iron-aluminum alloy may be added. If desired, more aluminum may be added, but it will be found that five pounds per ton will probably be suflicient in any case. This steel is processed in the usual way and the article is made therefrom. It is then subjected to cold work. This may be done by cutting the thread and thereafter subjecting it to the action of a. rolling or burnishing tool. On a drill pipe, for example, the tool may be used to apply cold work in an amount sufficient to reduce the diameter of the thread slightly, say about onethousandth of an inch. It will be found that by making the article of non-aging steel and subjecting it to cold work its qualities of resistance to fluctuating stress are greatly enhanced.

The accompanying figure of drawing illustrates part of a string of drill pipes. Each drill pipe has a body 2 and thickened end portions 3 exteriorly threaded as at 4 to accommodate couplings 5. On the drawing we have indicated the zone of cold work as extending over the threads. It will be understood that the couplings may be likewise cold worked and that if desired the cold working may extend over the entire article or over other selected parts thereof.

We have described a present preferred embodiment of our invention. It will be understood, however, that this is by way of illustration only and that it may be otherwise embodied or practiced within the scope of the following claims.

We claim:

1. As a new manufacture, a drill pipe made of substantially non-aging steel, the drill pipe being in the form of a. hollow tube having a thickened .end portion, which thickened end portion is threaded, the threaded portion at least being cold worked.

2.'As a new manufacture, a drill pipe made of substantially non-aging steel, the drill pipe being in the form of a hollow tube having a thickened end portion, which thickened end portion is threaded, the threaded portion at least being cold worked, and a coupling threaded to engage said end portion of the drill pipe, the coupling being made of substantially non-aging steel and being cold worked.

3. As a new manufacture, a metal body resistant to fluctuating stresses, the body being madeof non-aging steel and having at least a portion thereof of enhanced resistance to fluctuating stress, said portion being cold worked.

4. As a new manufacture, drill pipe made of substantially non-aging steel resistant to fluctuating stresses, at least a portion thereof being of enhanced resistance to fluctuating stress, said portion being cold worked.

5. As a new manufacture, a drill pipe made of substantially non-aging steel resistant to fluctuating stresses, the drill pipe having a threaded end portion of enhanced resistance to fluctuating stress, said end portion being cold worked.

HERBERT W. GRAHAM. SAMUEL L. CASE. 

